Most conversations around the San Francisco 49ers right now center around one question: Who should be the starting quarterback? There are legitimate arguments in favor of both Jimmy Garoppolo and Trey Lance. However, some of the discourse has been disconnected from logic. So let's examine the merit of the various arguments being made against Lance starting.
The fallacious arguments
The 49ers owe the starting job to Garoppolo
This is one of the more frustrating arguments I've heard. The 49ers don't "owe" the starting job to Garoppolo. They've paid him tens of millions of dollars over the last three seasons and have gotten average production from him. The NFL is about winning. Players who have given much more than Garoppolo has to the 49ers and are cut or benched all the time. That's the way it works. Garoppolo seems to have the personality through which he'd be able to take this in stride and still be a supportive member of the team.
Shanahan would lose the locker room if he named Lance the starter
This argument is ignorant at best. Very few people who are making this argument know what's going on in the 49ers' locker room and what the culture is like there. What we do have are quotes from veterans and coaches praising Lance's ability and maturity.
The recently-released Josh Rosen said Lance is "down to earth and did what coaches asked of him."
After their preseason game, Chiefs coach Andy Reid commented, "You're in good hands. He's a good player. He looked very poised."
Garoppolo himself said, "Trey's a good dude. He's pretty even-keeled for the most part."
It's still early, but it seems clear this isn't a Johnny Manziel/Dwayne Haskins situation.
No rookie quarterback has ever taken a team to the Super Bowl
No rookie quarterback has ever been in this strong of a position to do so. The 49ers have the best running game in the NFL, a top-5 coach, and a top-5 defense. Rookies as talented as Lance are almost always drafted to below-average teams and frequently terrible ones. The sample size of dynamic rookie quarterbacks on teams with legitimate Super Bowl aspirations is so tiny that it's not worth putting much weight into it.
Garoppolo has a better command of the offense
The offense Lance would be running would be different than the one Garopollo is running. Yes, many of the run concepts will be largely the same, but Shanahan's one of the more creative offensive minds in the NFL, and he would mold the offense to fit Lance's multi-dimensional skill set.
Flipping this the other way, if the 49ers have a devastating option-run/play-action offense with Lance at quarterback, would anyone be arguing that Garoppolo would be better suited to run that?
The fair arguments
Lance needs time to catch up to the speed of the NFL
The jump from North Dakota State to the NFL is dramatic, especially after only playing one game last season. The defenses Lance will be playing against will be faster, stronger, and more complex. My big worry is that Lance will try to run the ball as he did in college, increasing the risk of injury. At North Dakota State, Lance often lowered his shoulder like a running back to pick up extra yardage while running the ball.
It would be easier to start with Garopollo and switch to Lance midseason than the other way around
While I think Lance is mature beyond his years, he's still only 21 years old, and confidence is a fragile and fickle beast. If Lance was named the Week 1 starter and then benched midseason, it's fair to wonder how that would affect him for the rest of the season. The 49ers are a team with playoff and Super Bowl aspirations, after all. That's when they will need him.
Conclusion
Ultimately this isn't a mutually exclusive decision. Lance can be worked in gradually via different packages. But this decision should be based on who gives the 49ers the best chance to win, not some nebulous idea of fairness or barely relevant historical precedent.